Diagnostic Instructions

DTC Descriptors

DTC P0121: Throttle Position (TP) Sensor 1 Performance

DTC P0122: Throttle Position (TP) Sensor 1 Circuit Low Voltage

DTC P0123: Throttle Position (TP) Sensor 1 Circuit High Voltage

DTC P0221: Throttle Position (TP) Sensor 2 Performance

DTC P0222: Throttle Position (TP) Sensor 2 Circuit Low Voltage

DTC P0223: Throttle Position (TP) Sensor 2 Circuit High Voltage

Diagnostic Fault Information

Circuit	Short to Ground	Open/High Resistance	Short to Voltage	Signal Performance
5-Volt Reference	P0122, P0222, P0697, P2127	P0121, P0122, P0221, P2101, P2176	P0223, P0697, P2101, P2119, P2128, P2138	P0121, P0221, P0697
TP Sensor Signal 1	P0122	P0122	P0123	P0121
TP Sensor Signal 2	P0222	P0222	P0223, P0638, P2128, P2138	P0221
Low Reference	--	P0121, P0123, P0221, P0223, P2176	P0123, P0223*	P0121, P0221
* Internal ECM or TP sensor damage may occur if the circuit is shorted to B+

Typical Scan Tool Data

TP Sensor

Circuit	Short to Ground	Open	Short to Voltage
Operating Conditions: The engine is operating in closed loop Parameter Normal Range: TP Position Sensor 5%/4.2 Volts
5-Volt Reference	124%/0.0 Volts	7%/0.00 Volts	113%/TP 1 4.98 Volts, TP 2 4.50 Volts
TP Sensor Signal 1	4%/0.00 Volts	7%/0.00 Volts	7%/0.00 Volts
TP Sensor Signal 2	4%/0.00 Volts	4%/4.98 Volts	27%/4.980 Volts
Low Reference	--	0%/4.98 Volts	--

Circuit/System Description

The throttle body assembly contains 2 throttle position (TP) sensors. The TP sensors are mounted to the throttle body assembly and are not serviceable. The TP sensors provide a signal voltage that changes relative to throttle blade angle. The engine control module (ECM) supplies the TP sensors with a common 5-volt reference circuit , a common low reference circuit, and two independent signal circuits. The TP sensors have opposite functionality . TP sensor 1 signal voltage decreases from above 4 volts at idle to below 1 volt at wide open throttle (WOT). TP sensor 2 signal voltage increases from below 1 volts at idle to above 4 volts at WOT.

Conditions for Running the DTC

P0121

P0122, P0123, P0222, and P0223

P0221

Conditions for Setting the DTC

P0121

The TP sensor 1 disagrees by more than 6 percent from TP sensor 2 for greater than 1 second, and TP sensor 1 disagrees more than 9 percent from the predicted value for greater than 1 second.

P0122

The ECM detects the TP sensor 1 signal voltage is less than 0.18 volt for greater than 1 second.

P0123

The ECM detects the TP sensor 1 signal voltage is more than 4.6 volts for greater than 1 second.

P0221

The TP sensor 1 disagrees more than 6 percent from TP sensor 2 for greater than 1 second, and TP sensor 2 disagrees more than 9 percent from the predicted value for greater than 1 second.

P0222

The ECM detects the TP sensor 2 signal voltage is less than 0.16 volt for greater than 1 second.

P0223

The ECM detects the TP sensor 2 signal voltage is greater than 4.9 volts for greater than 1 second.

Action Taken When the DTC Sets

Conditions for Clearing the DTC

Diagnostic Aids

If there is a condition with the TP sensors the ECM defaults to reduced power mode for the entire ignition cycle, even if the condition is corrected.

Reference Information

Schematic Reference

Engine Controls Schematics

Connector End View Reference

Electrical Information Reference

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Circuit/System Verification

1. Ignition ON, observe the DTC information with a scan tool. DTC P0697 should not be set.

⇒	If a DTC is set, refer to DTC P0697 .

2. Ignition ON, clear the DTC Info with a scan tool.
3. Start the engine, observe the scan tool TP Sensor 1 and 2 voltage parameters. TP sensor 1 should be between 0.17-4.6 volts and TP sensor 2 should be between 0.15-4.8 volts.
4. Observe the scan tool TP sensor 1 and 2 parameters while performing the following tests:

•	Rapidly depress the accelerator pedal from the rest position to the wide open throttle position (WOT) and release pedal. Repeat the procedure several times.

•	Slowly depress the accelerator pedal to WOT and then slowly return the pedal to closed throttle. Repeat the procedure several times.

•	The scan tool TP sensor 1 and 2 parameters should display Agree.

5. Observe the DTC Information with a scan tool. DTCs P0121, P0122, P0123, P0221, P0222, and P0223 should not set.

Circuit/System Testing

1. Ignition OFF, remove the fuse that supplies B+ to terminal C2-56 of the ECM.
2. Disconnect the throttle body harness connector.

Important: The control module or the sensor may be damaged if the circuit is shorted to battery positive voltage.

3. Test for 5 ohms or less between the low reference circuit terminal C and ground.

⇒	If greater than the specified value, test the low reference circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the ECM.

4. Install fuse that supplies B+ to terminal C2-56 of the ECM.
5. Ignition ON, load test for 4.8-5.2 volts between the test lamp probe connected to the 5-volt reference circuit terminal E and ground.

Important: The 5-volt reference circuits are internally and externally connected at the ECM. Other component DTCs may be set. If other DTCs are set, review the electrical schematic and diagnose the applicable circuits and components.

⇒	If less than the specified range, test the 5-volt reference circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the ECM.

⇒	If greater than the specified range, test the 5-volt reference circuit for a short to voltage. If the circuit tests normal, replace the ECM.

6. Ignition ON, verify that the scan tool TP sensor 1 voltage parameter is less than 0.3 volt.

⇒	If greater than the specified range, test the signal circuit for a short to voltage. If the circuit tests normal, replace the ECM.

7. Connect a 3A fused jumper wire between the 5 volt reference circuit terminal E and the TP sensor 1 signal circuit terminal D. Verify the TP sensor 1 voltage parameter is greater than 4.89 volts.

⇒	If less than the specified value, test the signal circuit for an open/high resistance or for a short to ground. If the circuit tests normal, replace the ECM.

8. Verify the TP sensor 2 voltage parameter is greater than 4.97 volts.

⇒	If less than the specified value, test the signal circuit for a short to ground. If the circuit tests normal, replace the ECM.

Important: If the fuse in the jumper wire opens, the signal circuit is shorted to a voltage.

9. Connect a 3A fused jumper wire between the TP sensor 2 signal circuit terminal F and the low reference circuit terminal C. Verify the scan tool TP sensor 2 voltage parameter is less than 0.10 volts.

⇒	If greater than the specified value, test the signal circuit for an open/high resistance or for a short to voltage. If the circuit tests normal, replace the ECM.

10. If all circuits test normal, test or replace the throttle body assembly.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.